One of the many threats loggerhead sea turtles face is man-made pollution, but the extent of the risk is a question. To begin to look for the answer scientists have measured contaminants in the blood of a group of adult male turtles and tracked their migration along the Atlantic Coast.

http://graphics8.nytimes.com/images/global/icons/rss.gif Get Science News From The New York Times » (http://www.nytimes.com/services/xml/rss/nyt/Science.xml)

The group, led by Jared M. Ragland, a graduate student at the College of Charleston, in Charleston, S.C., captured 19 loggerheads near Cape Canaveral, Fla., in 2006 and 2007. Group members measured and weighed the turtles, took blood samples, and examined their reproductive systems with testicular biopsies. Then they fitted them with satellite transmitters and released them. Over two months, 10 of the animals traveled north as far as Cape May, N.J., while nine remained near Cape Canaveral.
The study (http://onlinelibrary.wiley.com/doi/10.1002/etc.540/abstract), published in the journal Environmental Toxicology and Chemistry, found that the animals had measurable blood levels of 67 different chemicals used in pesticides (http://health.nytimes.com/health/guides/nutrition/pesticides/overview.html?inline=nyt-classifier) and other industrial products. The loggerheads that migrated had higher levels than those that stayed near Florida, confirming prior research that found more pollutants in turtles in northern latitudes.
It is possible that the fish and invertebrates that turtles feed on in northern waters are more polluted, but the scientists point out that turtles that migrate eat more, and therefore consume more pollutants. Migrating turtles were on average larger than the permanent residents.
The animals seemed healthy, researchers said, but what constitutes good health in an adult male loggerhead is not clear. “These were reproductively active animals,” said Jennifer M. Keller, a co-author of the study and a biologist with the National Institute of Standards and Technology (http://topics.nytimes.com/top/reference/timestopics/organizations/n/national_institute_of_standards_and_technology/index.html?inline=nyt-org). “But the males have higher blood levels of contaminants than the juveniles, and that adds to our concern.”

A version of this article appeared in print on April 26, 2011, on page D3 of the New York edition with the headline: Migrating Sea Turtles Pick Up More Pollution.